Tetralogy of Fallot and cyanotic congenital heart disease

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Unrepaired tetralogy presents with cyanosis and spells in infancy, but anatomy and prior palliation vary. Adult care must start with the operative history and current anatomy rather than assuming a uniform repair.

Chronic pulmonary regurgitation after transannular-patch repair can be well tolerated for years while the RV progressively enlarges. Timing of pulmonary-valve replacement integrates symptoms, CMR volumes, RV/LV function, exercise capacity and arrhythmia.

Key points

Tetralogy comprises VSD, overriding aorta, right-ventricular outflow obstruction and right-ventricular hypertrophy.
Severity of RV outflow obstruction determines the degree of right-to-left shunt and cyanosis.
Squatting or knee-to-chest positioning raises systemic vascular resistance and can reduce right-to-left shunting during a hypercyanotic spell.
Most UK adults are repaired; important late problems include pulmonary regurgitation, RV dilatation/dysfunction, residual RVOT obstruction, atrial arrhythmia and ventricular tachycardia.
A right bundle branch block pattern is common after repair; progressive QRS prolongation is a risk marker but never a stand-alone ICD indication.
CMR is central for RV volumes, function and pulmonary regurgitant fraction.
All repaired tetralogy patients need lifelong expert ACHD follow-up, even when asymptomatic.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Conotruncal maldevelopment

Anterior malalignment of the outlet septum during cardiac development creates the ventricular septal defect, overriding aorta and right-ventricular outflow narrowing that define tetralogy.

Genetic susceptibility

Chromosomal or single-gene disorders can disturb outflow-tract development. Syndromic features, other congenital anomalies or an affected family history therefore support specialist genetic assessment.

Unrepaired or palliated anatomy

Adults with unrepaired disease or earlier palliative shunts retain variable obstruction and right-to-left flow. Their physiology depends on the native anatomy and every previous procedure.

Post-repair valve injury

A transannular patch, pulmonary valvotomy or right-ventricular outflow reconstruction relieves obstruction but may leave important pulmonary regurgitation, often a dominant late adult lesion.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Outlet malalignment
The displaced outlet septum narrows the right-ventricular outflow, leaves a large ventricular communication and positions the aortic root over both ventricles.
2
Right-ventricular pressure load
Ejection against the narrowed outflow raises right-ventricular pressure and produces hypertrophy. The degree of obstruction, rather than the septal defect alone, largely determines the right-to-left shunt and cyanosis.
3
Right-to-left shunting
The large ventricular defect tends to equalise ventricular systolic pressures, while outflow obstruction diverts part of right-ventricular output through the defect into the overriding aorta. Greater obstruction or lower systemic vascular resistance increases this right-to-left shunt and central cyanosis.
4
Hypercyanotic escalation
A sudden increase in outflow obstruction or fall in systemic resistance intensifies right-to-left shunting. Pulmonary flow falls, cyanosis deepens and the obstruction murmur may soften.
5
Late repaired physiology
Chronic pulmonary regurgitation volume-loads and dilates the right ventricle, while operative scar and residual obstruction create substrates for dysfunction and atrial or ventricular arrhythmia.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Unrepaired physiology

Central cyanosis, clubbing, RV heave and an ejection systolic murmur from RVOT obstruction; a single S2 may be heard.

Hypercyanotic spellRed flag

Sudden deepening cyanosis, tachypnoea, agitation or syncope from increased right-to-left shunting; the RVOT murmur may soften as flow falls.

Pulmonary regurgitation after repair

Reduced exercise capacity, right-sided dilatation, early diastolic murmur and progressive RV dysfunction.

Late arrhythmiaRed flag

Palpitations, presyncope or syncope may reflect atrial tachycardia or scar-related monomorphic VT.

Endocarditis or conduit failure

Fever, new murmur, embolic signs or abrupt deterioration in a prosthetic conduit/valve needs urgent investigation.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
12-lead ECG and ambulatory monitoringFirst step
Why
Assess conduction, QRS duration and atrial/ventricular arrhythmia.
Interpretation and limitations
Post-repair RBBB is common; interpret QRS trends with RV size, scars, symptoms and rhythm findings.
02
Transthoracic echocardiography
Why
Assess residual VSD, RVOT gradient, pulmonary/tricuspid regurgitation, RV/LV function and aortic root.
Interpretation and limitations
Echo may underestimate RV volumes; use CMR for quantitative surveillance.
03
Cardiac MRI
Why
Quantify RV/LV volumes, ejection fraction, pulmonary regurgitation, RVOT anatomy and scar.
Interpretation and limitations
Serial trends help time pulmonary-valve intervention before irreversible RV dysfunction.
04
Cardiopulmonary exercise testing
Why
Objectively measure exercise capacity and haemodynamic response.
Interpretation and limitations
Decline may precede reported symptoms and supports integrated intervention decisions.
05
CT or invasive electrophysiology/catheter study
Why
Resolve coronary/conduit anatomy, haemodynamics or arrhythmic substrate when intervention is planned.
Interpretation and limitations
Coronary course must be defined before RVOT or transcatheter pulmonary-valve intervention.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Eisenmenger physiology

Cyanosis follows longstanding pulmonary vascular disease and reversal of a previously left-to-right shunt. Echocardiography shows high pulmonary pressure without tetralogy’s characteristic outflow anatomy.

Primary respiratory disease

Wheeze, crackles or parenchymal abnormalities with no congenital shunt may explain hypoxaemia. A spell with softer outflow murmur and abrupt deepening cyanosis favours cardiac shunting.

Pulmonary embolism

Sudden pleuritic pain, new hypoxaemia and acute right-heart strain can mimic congenital deterioration. Comparison with baseline saturation and targeted pulmonary vascular imaging helps discriminate.

Arrhythmic syncope

In repaired tetralogy, scar-related ventricular tachycardia may cause abrupt palpitations or syncope without a primary fall in oxygen saturation. Rhythm monitoring distinguishes it from a hypercyanotic spell.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01FirstAcute cyanotic deteriorationFirst stepSudden increased cyanosis, dyspnoea, agitation or collapse.

1Call for resuscitation help; assess airway, breathing, circulation, rhythm, saturation and glucose while giving oxygen for hypoxaemia.
2Keep the person calm, use knee-to-chest positioning when hypercyanotic physiology is suspected and obtain IV access without delaying stabilisation.
3Correct dehydration, anaemia/iron deficiency, infection, acidosis and arrhythmia; avoid abrupt systemic vasodilation.
4Transfer urgently to a congenital cardiac centre; use specialist-directed pharmacological or mechanical support if the spell persists.

02NextRoutine repaired-tetralogy reviewAny adult after tetralogy repair, symptomatic or not.

1Reconstruct anatomy and operations, then assess symptoms, rhythm, saturation, examination and ECG trends.
2Perform expert echo and periodic CMR, with exercise testing to detect silent functional decline.
3Assess pulmonary regurgitation/RVOT obstruction, biventricular function, residual VSD, aortic root and arrhythmia together.
4Set an ACHD follow-up interval and provide exercise, pregnancy, endocarditis and emergency advice.

03EscalationPulmonary-valve or arrhythmia interventionEscalationSymptoms, severe pulmonary regurgitation/RVOT obstruction, progressive RV enlargement or dysfunction, declining exercise capacity or sustained arrhythmia.

1Discuss in a combined ACHD imaging, interventional, surgical and electrophysiology multidisciplinary team.
2Define CMR volumes/function, coronary anatomy, RVOT/conduit anatomy and arrhythmia substrate.
3Choose surgical or transcatheter pulmonary-valve replacement and address residual lesions or arrhythmic isthmuses as appropriate.
4Consider ICD therapy only after comprehensive sudden-death risk assessment; continue surveillance after intervention.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Right-ventricular dilatation and failure

Chronic pulmonary regurgitation produces progressive volume overload that may remain silent while the right ventricle enlarges and loses contractile function, potentially leading to systemic venous congestion.

Residual outflow obstruction

Persistent or recurrent right-ventricular outflow narrowing maintains a pressure load, limiting exercise and accelerating hypertrophy or dysfunction even after an apparently successful childhood repair.

Atrial and ventricular arrhythmia

Atrial enlargement, ventricular scar and patch borders permit re-entry. Sustained ventricular tachycardia can cause syncope or sudden death, while atrial tachycardia may worsen haemodynamics.

Endocarditis and conduit failure

Residual jets, prosthetic pulmonary valves and conduits provide surfaces for infection or structural degeneration. Fever, a new murmur or abrupt deterioration therefore requires urgent reassessment.

Paradoxical embolism

Persistent right-to-left shunting allows venous thrombus or introduced air to bypass the pulmonary filter and enter systemic arteries, risking stroke or other organ infarction.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Lifelong ACHD visits with symptoms, oxygen saturation, examination and 12-lead ECG.
Serial echo plus periodic CMR for RV volumes/function and pulmonary regurgitation/RVOT obstruction.
Ambulatory rhythm monitoring for palpitations, syncope, QRS progression or other arrhythmic risk markers.
Objective exercise testing at intervals to identify declining capacity.
Pre-pregnancy Pregnancy Heart Team review and an individual exercise plan; avoid unreviewed high-intensity sport when significant residual disease exists.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

A quieter murmur can be worse

During a hypercyanotic spell, falling RVOT flow can soften the obstruction murmur as right-to-left shunting increases.

Pulmonary regurgitation is a volume lesion

Symptoms can lag behind marked RV enlargement, which is why CMR surveillance matters.

QRS is contextual

A broadening QRS reflects conduction/scar and often RV dilatation, but risk assessment also needs ventricular function, symptoms and arrhythmia.

Know the coronary course

An anomalous coronary crossing the RVOT can determine the safety and type of pulmonary intervention.

Cyanosis changes routine care

Air filters on IV lines, meticulous hydration and specialist planning reduce paradoxical embolic and haemostatic complications.

11Common pitfallsFrequent interpretation and management errors.

01
Assuming childhood repair is curative and discharging from ACHD care.
02
Relying on symptoms alone to time pulmonary-valve replacement.
03
Treating a hypercyanotic spell as primary lung disease while the murmur becomes quieter.
04
Using QRS duration alone to decide on an ICD.
05
Planning RVOT intervention before defining coronary anatomy.